Sudden cardiac death is the leading cause of death in the United States, with one person dying every two minutes and 70% of those deaths occurring in the home. Most sudden cardiac death is caused by ventricular fibrillation ("VF"), in which the heart's muscle fibers contract without coordination, thereby interrupting normal blood flow to the body. The only known effective treatment for VF is electrical defibrillation, in which an electrical pulse is applied to the patient's heart. The electrical pulse must be delivered within a short time after onset of VF in order for the patient to have any reasonable chance of survival. Electrical defibrillation may also be used to treat shockable ventricular tachycardia ("VT"). Accordingly, defibrillation is the appropriate therapy for any shockable cardiac rhythm, i.e., VF or shockable VT.
One way of providing electrical defibrillation uses an external defibrillator. External defibrillators send electrical pulses to the patient's heart through electrodes applied to the patient's torso. External defibrillators are typically located and used in hospital emergency rooms, operating rooms, and emergency medical vehicles. Of the wide variety of external defibrillators currently available, automatic and semi-automatic external defibrillators (referred to collectively as "AEDs") are becoming increasingly popular because they can be used by relatively inexperienced personnel. Such AEDs are also especially lightweight, compact, and portable. AEDs are described in U.S. Pat. No. 5,607,454 to Cameron et al. entitled "Electrotherapy Method and Apparatus" and PCT Publication No. WO 94/27674 entitled "Defibrillator with Self-Test Features", the specifications of which are incorporated herein.
AEDs provide a number of advantages, including the availability of external defibrillation at locations where external defibrillation is likely to be performed quite infrequently, such as in residences, public buildings, businesses, personal vehicles, public transportation vehicles, etc. AEDs contain an algorithm that enables the device to determine whether the victim has a shockable rhythm. Thus, the AED obviates the need for a trained user to interpret the ECG. Further, AEDs prompt the user in the correct protocol for administering care. For first tier responder (such as flight attendants and security guards), a device that delivers prompts with specific instructions is most effective. In this use model, because of the detailed prompting, the AED drives the patient care protocol.
One example of prompting provided by an AED is delivered by ForeRunner.RTM. by Heartstream. When a user turns the device on, the device prompts the user to "APPLY PADS." Once the electrode pads have been attached, the device will indicate to the user "ANALYZING HEART RHYTHM--DO NOT TOUCH THE PATIENT." Once the device determines that a shockable heart rhythm is present the device then prompt the user to "DELIVER SHOCK NOW--PRESS THE ORANGE BUTTON." After delivering the shock, the device then prompts "SHOCK DELIVERED--IT IS SAFE TO TOUCH THE PATIENT, CHECK AIRWAY, CHECK BREATHING, CHECK PULSE, IF NEEDED, BEGIN CPR." Other prompts may be delivered as well, depending on the set-up of the device and the condition of the patient.
One drawback to using an AED is that the prompts are designed for a lay responder and there is no way to alter or disable the prompts during use in an emergency without changing the underlying operation of the AED. Thus when a more advanced caregiver arrives at the scene of an emergency (such as an EMT or paramedic), he or she may not wish to disconnect the victim from the AED and attach a paramedic defibrillator (which may also include the ECG analysis but only features limited prompts) since there is a possibility that the victim will revert into sudden cardiac arrest during the time that the AED is removed and prior to the time another device is attached. Additionally there would be a discontinuity to any ECG data that was collected for the victim since the initial data would be recorded by the first responder AED and subsequent data would be recorded by the paramedic defibrillator. However, second tier responders typically have additional training and are more likely to drive the patient care protocol. As a result, the advanced caregiver will not need or want to be given the detailed prompting by the AED. However, the only way to disable the prompts in an AED is to turn the device off. Thus, if the device is left on, the advanced caregiver will be forced to listen to unnecessary and often distracting prompts.
Thus, when emergency response personnel are called to the scene of a cardiac arrest or a patient is transferred to the emergency room, the ability to inactivate the prompting feature of an AED is desirable. Further, it is desirable to inactivate the prompting features of an AED without inactivating the monitoring and analysis functionality of the AED.
Thus, it is an object of the present invention to provide medical personnel with an AED that allows the user to inactivate the prompting functionality of the device without inactivating the analysis algorithm.